This invention relates to a connection for attaching a mudsill or other frame member of a building structure to a foundation, by means of an adjustable foundation plate.
Earthquakes, hurricanes, tornadoes, floods or tidal action impose upward as well as lateral forces on a building structure that can lift it off its foundation. To counteract uplift and lateral forces, it has become standard practice to tie or anchor the structure to its concrete foundation.
Earthquake damage assessments show that a lack of foundation anchors is one of the two main earthquake failure modes for residential wood structures.
One of the first commercially accepted practices for anchoring a building structure to its foundation was to attach the horizontal frame member or mudsill to threaded anchor bolts embedded in the upper surface of the concrete foundation. There have been many inventions teaching improvements on this method. See U.S. Pat. No. 5,249,404, granted Oct. 5, 1993 to William F. Leek and Alfred D. Commins (patent teaching a connection formed with a metal holdown connector between the anchor bolt and a vertical frame member of the building structure). See U.S. Pat. No. 5,510,553, granted Sep. 29, 1992 to Alfred D. Commins and Ernest A. Romeo (patent teaching a connection formed with a strap that combines a holdown connector which attaches to a vertical frame member and an anchoring means which is embedded in the foundation to form a single piece for easier installation). However, these improved methods as well as the earlier method are not easily or economically adapted to connecting a completed building structure to its foundation. First, these connections require the anchor to be set when the foundation is poured. Secondly, they call for an anchor that protrudes from the upper surface of the foundation which is best installed before the building structure is constructed on the foundation.
The purpose of the present invention is to easily and economically form a strong connection between a frame member of a completed building structure and the foundation on which it rests.
Retrofit work imposes two major difficulties on the builder. The builder must add the connection to an existing structure and he must work in what is very often a cramped space underneath the building structure. The ease with which this connection can be formed despite these difficulties is important to its economic success, and, in fact, the ease of installation of the connection may be determinative as to whether the retrofit work will be done at all. This is especially true for crawl space foundations, where it is not uncommon that the installer will find himself slithering around on his belly in the dirt amid the black widow spiders and every imaginable type of refuse left by the workman who built the original house, including nails, screws, glass, pieces of wire, stones, pieces of concrete, and pieces of plasterboard.
The first specific problem in such retrofit work is that access to the top face of the foundation is restricted since the frame member sits on it and there is usually little clearance between other members of the building structure, such as floor joists, and the top face of the foundation. Thus there is a great need for methods for retrofitting that allow the workman to install the anchoring means to the exposed side face of the foundation rather than the top face of the foundation.
Secondly, the dimensions of frame members and foundations are rarely uniform. The width of the frame member and the width of the foundation will vary. While it is usual to expect that the frame member, such as the mudsill, will be thinner than the foundation, it is not uncommon to find structures where the mudsill member is wider than the foundation and overhangs the foundation.
Thirdly, it has been found that in a substantial number of buildings, the mudsill is incorrectly installed on the foundation so that it overhangs the foundation.
Fourthly, in a substantial number of foundations, the mudsill may rest totally on the foundation, but the mudsill is not parallel to the inside face of the foundation.
Fifthly, some buildings have been encountered where the mudsill not only overhangs the foundation, but also is out of alignment with the inside face of the foundation.
Thus an economically viable solution for making this connection as a retrofit, must be able to adapt easily to the differing dimensions and construction practices.
Finally, because the dimensions of frame members and foundations are variable within even a single building structure, the installer will have to individually adjust each connector to fit the dimensions of the frame member and the foundation while he is installing it in the cramped space under the building structure. This means that the adjustable foundation plate connector must be easily adapted to installations of differing dimensions.
U.S. Pat. No. 1,078,142, granted Nov. 11, 1913, to Charles Hamann, teaches a device for anchoring structures to a concrete base that can be adjusted to allow for shrinkage of the structure anchored thereby. However, U.S. Pat. No. 1,078,142 is not suitable for retrofit work as the invention teaches that the foundation fastener means should project above the top of the upper surface of the foundation.
U.S. Pat. 5,072,570, granted Dec. 17, 1991 to Michael. Johnson, teaches a method for anchoring an existing wood frame building to its foundation with elongated truss members. Requiring the use of elongated truss members limits the application of this patent to foundations where access to the frame member and foundation is unhindered. Furthermore, to accommodate installations where the side face of the frame member, such as the sill plate, does not align with the side face of the foundation member, the installer must custom fashion either an additional framing member or plate to span the distance between the elongated truss member attached to the side face of the foundation and the side face of the frame member.
A product on the market, the Harlen Retrofit Foundation System, patent pending, teaches a method for anchoring an existing wood frame building to its foundation with small, adjustable sheet metal connectors. The Harlen device achieves an adjustable connector by having two attachment members that slide in relation to each other and attach by inserting a held-holding fastener means into a discrete selected opening among a plurality of discrete openings. The fact that these openings receive the held-holding fastener means in close registration and the fact that they occur at various positions on both the frame attachment member and the foundation attachment member makes adjustment of the sheet metal connector difficult, especially when in a cramped space.
For example, in Harlen, the workman must align his top and bottom plates so that out of the twenty eight (28) openings in the upper plate, only two of them will be in alignment with two out of the six holes in the bottom plate. Fitting two bolts into the two openings which are in alignment is not too difficult when you can look down upon the top plate and can see which holes are in alignment. Consider, however, how difficult this task is when there is not enough room as illustrated in FIG. 2 to get your head between the top of the foundation 1, the subfloor 71, and the floor joists 72. In this situation, the workman cannot see which two openings are in alignment, so he must find the proper hole out of fourteen (14) different holes by actually trying them one at a time. After he finds matching holes, he must then repeat the process in the other fourteen (14) holes. Playing this adult version of a game we all played in kindergarten by a workman for several days in a dark and dirty crawl space could drive a good man to strong drink.
The Harlen device also can not be used in installations where the frame member substantially overhangs the side surface of the foundation.